Field of the Invention
This invention relates to a pre-assembly muff for fitting a cutting or clamping ring of a pipe coupling, which comprises an inner cone which is designed to support the ring slid on to the pipe and into which the ring may be pressed.
In the case of pipe couplings, depending on the type of coupling, clamping rings or cutting rings are frequently not fitted on the pipe during the final pipe assembly, but they are pre-assembled in advance. The special purpose of this measure is to ensure a functionally accurate connection between the pipe and the clamping or cutting ring. The rings are pre-fitted by using a pre-assembly muff. The pre-assembly muffs used are suitable for being operated by hand or by an assembly machine.
However, such pre-assembly muffs have a problem in that the surface of the inner cone is subject to wear with the resulting disadvantage of causing the dimensions of the inner cone to change. If the diameter of the conical face increases, the axial travel of the clamping or cutting ring appears to be greater than actually required in order to achieve the connection. But for the fitter it is not always immediately obvious that the permissible service life has already been exceeded. To be able to operate with safe conditions he would have to arrange for the inner conical face of the pre-assembly muff to be measured. This is a complicated and expensive process. Furthermore, an inaccurate or improper assembly leads to leakages and unfastening of the connection.
It is therefore the object of the present invention to provide a pre-assembly muff which makes it possible for the user to identify the end of the service life of the muff without there being any need for additional checks in the form of measurements.